1. Field Of The Invention
The invention relates to a hydroprocessing a petroleum distillate in an ebullated bed reactor.
2. Description Of Other Related Methods In The Field
Hydroprocessing is used in petroleum refineries to hydrogenate petroleum derived stocks. Hydrogenation removes sulfur, nitrogen, metals and other undesirable contaminants from the stock. Hydrogenation also saturates olefinic and aromatic compounds rendering the stock more stable to thermal degradation as well as stabilizing color. Hydroprocessing at more severe conditions is used to both hydrogenerate stocks as well as effect mild hydrocracking.
Hydroprocessing is typically carried out in a packed bed of catalyst. Hydroprocessing catalysts typically comprise a Group VI metal or a Group VIII metal such as nickel, cobalt or molybdenum on a porous solid support. Cobalt-molybdenum and nickel-molybdenum on an aluminum support are in wide commercial use in the industry for this purpose. The hydroprocessing reaction is carried out at a hydrogen partial pressure of 100 psia (6.8 atm) to 3000 psia (204 atm) and a temperature of 400.degree. F. (204.degree. C.) to 850.degree. F. (454.degree. C.).
A fixed bed hydrotreater typically comprises a charge pump, a make-up hydrogen compressor, feed/effluent and hydrogen/effluent heat exchanges, a charge heater, one or more reactors, product separators, a recycle hydrogen compressor and product fractionators.
An advancement in the art of packed bed hydrotreating is described in U.S. Pat. No. 5,039,396 to R. M. Steinberg et al.
The ebullated bed process comprises the passing of concurrently flowing streams of liquids or slurries of liquids and solids and gas upwardly through a vertically elongated cylindrical vessel containing a catalyst bed. The catalyst in the bed is maintained in random motion in the liquid and has a gross volume dispersed through the liquid greater than the volume of the catalyst when stationary. This technology has been used commercially in the upgrading of heavy liquid hydrocarbons or converting coal to synthetic oils.
The process is generally described in U.S. Pat. No. 25,770 to Johanson incorporated herein by reference. A mixture of hydrocarbon liquid and hydrogen is passed upwardly through a bed of catalyst particles at a rate such that the particles are forced into random motion as the liquid and gas flow upwardly through the bed. The random catalyst motion is controlled by recycle liquid flow so that at steady state, the bulk of the catalyst does not rise above a definable level in the reactor. Vapors along with the liquid which is being hydrogenated are removed at the upper portion of the reactor.
The ebullated bed process has been found to be applicable to hydrocracking petroleum derived hydrocarbon distillate fractions. U.S. Pat. No. 5,108,580 to G. Nongbri et al. teaches an ebullated bed for hydrocracking a heavy vacuum gas oil fraction. This distillate fraction is recycled to extinction between an ebullated bed hydrocracker and a fluid catalytic cracker (FCC).